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E. H. Lloyd D. Warren 《Stochastic Environmental Research and Risk Assessment (SERRA)》1988,2(3):175-188
It was remarked by Hurst in 1951 that the adjusted range gives the size of the smallest reservoir capable of providing a constant discharge equal to the mean inflow. Since that time this range and its rescaled modification, the Hurst range, have been widely discussed, not however primarily with a view to applying them to reservoir design problems, but rather on account of their possible relevance to the simulation of geophysical time series.Acknowledging the well-known conceptual weaknesses of adjusted ranges and the theoretical difficulties that inhibit their direct utilisation in the design and operation of real reservoirs, the authors argue that the interest displayed on ranges during the past few decades justifies the effort of eliminating one in particular of these weakness, namely their non-implementability as operating policies, a consequence of the fact that they can only be retrospectively evaluated. The paper proposes modifications in which the unknowable mean and standard deviation of future samples are replaced by the known mean and sample standard deviation of historical data, leading to the historically adjusted range and the historically rescaled and adjusted range. The latter is produced as an implementable approximation to Hurst's (1951) solution to the optimal reservoir problem.The expected values of the new ranges are evaluated and numerically tabulated. 相似文献
2.
城市建设用地遥感信息提取方法研究 总被引：4，自引：0，他引：4
本文利用CBERS-02B影像,通过分析各个地类的光谱特征,发现了长沙市城市建设用地和其他背景地物的区别,并在此基础上选取了土壤调节植被指数(SAVI)、归一化水体指数(NDWI)和比值居民地指数(RRI)作为三个指数波段,重新进行波段组合,从而减少了波段数据的冗余,最后采用最大似然法分类,提取出城市建设用地信息,其正确率达到85.6%。 相似文献
3.
基于MSAVI-WI特征空间的新疆渭干河-库车河流域绿洲土壤盐渍化研究 总被引：5，自引：0，他引：5
土壤盐渍化是造成干旱区土地荒漠化及生态恶化的重要原因,及时获取大尺度高精度土壤盐渍信息是防治工作的基础。选取新疆塔里木盆地北缘渭干河—库车河流域三角洲绿洲为研究区,利用Lansat-TM数据与野外实测数据分析盐渍化土壤与修改型土壤调整植被指数(MSAVI)、湿度指数(WI)之间的关系,在此基础上提出了MSAVI-WI特征空间概念,构建了土壤盐渍化遥感监测指数模型(MWI)。结果表明:MWI与土壤表层含盐量相关性较高,其相关性为0.844,精度高于土壤盐渍监测常用的盐分指数与实测数据的相关性。MWI能较好的反映盐渍化土壤地表植被及土壤水分的组合变化,具有明确的生物物理意义,并且特征参量简单,理论上易于理解,实践上易于实现,MWI模型的构建有利于干旱区大尺度土壤盐渍化定量监测与评价工作的开展。 相似文献
4.
Guangyong You Yiping Zhang Yuhong Liu Qinghai Song Zhiyun Lu Zhenghong Tan Chuansheng Wu Youneng Xie 《水文研究》2013,27(18):2676-2682
Negative trends of measured pan evaporation are widely reported. Studies of the factors that underlie this reduction in pan evaporation have not reached a consensus about the controlling factors. Most studies employ statistical analysis (correlation analysis or stepwise regression) to identify the controlling climatic variables; in contrast, few studies have employed physical‐based theories. In addition, observations of pan evaporation and related climatic variables are reported to be influenced by anthropogenic activities. Consequently, the observed trends of climatic variables in a nature reserve would be useful for understanding regional climate change. The present study site is located in Ailaoshan National Nature Reserve, SW China, which is free of anthropogenic activity. In this study, we firstly applied the adjusted PenPan model to estimate the pan evaporation. Then, using this physical‐based model, we identified a positive trend in pan evaporation, with a much larger increase in the dry season than in the wet season. The model results indicate that the change in the aerodynamic component is larger than that in the radiative component. In contrast to the reduction in wind speed and sunshine hours that has been reported in previous studies at various sites, we found that wind speed and sunshine hours have increased in recent decades, thereby explaining the increase of the pan evaporation rate. Wind speed made the greatest contribution to the change in pan evaporation, followed by sunshine duration. This study indicates that the potential evaporation has increased at this site despite the widely reported reduction in measured pan evaporation. During the dry season, the availability of water for agriculture and agroforestry could be threatened. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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基于DEM的山区气温空间模拟方法 总被引：57，自引：3，他引：57
气温作为一种农业资源是由太阳辐射到达大气形成的，在地球表面的分布地地表的地形特征密不可分（特别在山区）。数字高程模型（Digital Elevation Model，简称DEM）作为一种地表形态的描述方式，在利用空间信息进行各种专题分析研究和规划决策过程中具有很大的实用价值。研究提出了以地理信息系统（GIS）为支撑，在常规统计模型（CSM）的基础上，利用地形的坡度、坡向因子进行山区气温空间小尺工模拟的修正模型－－地形调节统计模型（TASM），并在环青海湖地区进行实际应用。研究结果表明，地形调节统计模型优于常规的统计模型，从而为山区任一地域单元气温空间分布的快速计算提供了一种可行的方法，对山区气温资源的专题应用具有重要的意义。 相似文献
6.
选用蒙城地震台2001年1月到2007年12月的456个地震,与中国地震台网中心提供的《中国地震大震速报目录》进行面波震级的对比,得出蒙城地震台的台基校正值、标准误差,并进一步分析了两者之间的相关性、一致性,对蒙城地震台单台面波震级的准确测定提供了重要的参考依据。 相似文献
7.
顾及方向遮蔽性的反距离权重插值法 总被引：1，自引：0，他引：1
针对反距离权重(IDW)空间插值在实际应用中存在的缺陷,本文对IDW插值算法进行了优化改进,提出了调和反距离权重(AIDW)空间插值方式。该插值方式在传统IDW的算式中增加了反映样点方位的调和权重系数K,其插值过程综合考虑了样点距离和样点方位对插值点的共同影响。理论分析和实例应用表明:AIDW插值方式可减小或克服样点分布不均的IDW插值缺陷,使离散点的空间插值结果更趋于合理,其等值线绘制亦可有效避免传统IDW插值中的孤立圆及同心圆现象,使等值线的绘制更接近于人工作业。 相似文献
8.
Abdou Abouelmagd Mohamed Sultan Neil C. Sturchio Farouk Soliman Mohamed Rashed Mohamed Ahmed Alan E. Kehew Adam Milewski Kyle Chouinard 《Quaternary Research》2014
Sixteen groundwater samples collected from production wells tapping Lower Cretaceous Nubian Sandstone and fractured basement aquifers in Sinai were analyzed for their stable isotopic compositions, dissolved noble gas concentrations (recharge temperatures), tritium activities, and 14C abundances. Results define two groups of samples: Group I has older ages, lower recharge temperatures, and depleted isotopic compositions (adjusted 14C model age: 24,000–31,000 yr BP; δ18O: − 9.59‰ to − 6.53‰; δ2H: − 72.9‰ to − 42.9‰; < 1 TU; and recharge T: 17.5–22.0°C) compared to Group II (adjusted 14C model age: 700–4700 yr BP; δ18O: − 5.89‰ to − 4.84‰; δ2H: − 34.5‰ to − 24.1‰; < 1 to 2.78 TU; and recharge T: 20.6–26.2°C). Group II samples have isotopic compositions similar to those of average modern rainfall, with larger d-excess values than Group I waters, and locally measurable tritium activity (up to 2.8 TU). These observations are consistent with (1) the Nubian Aquifer being largely recharged prior to and/or during the Last Glacial Maximum (represented by Group I), possibly through the intensification of paleowesterlies; and (2) continued sporadic recharge during the relatively dry and warmer interglacial period (represented by Group II) under conditions similar to those of the present. 相似文献
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10.
基于中国站点网气候资料,简要介绍了经验正交函数(empirical orthogonal function,EOF)与改进的经验正交函数(adjusted EOF,AEOF)分析方法的关系,给出了验证其分析效果的方案;并将EOF、AEOF分析方法应用于中国160站60 a(1951—2010年)夏季气温距平场序列的分析。结果表明:AEOF分析方法前6个模态的模方拟合率和累积模方拟合率均高于EOF分析方法的相应量;AEOF分析方法前3个模态的典型场对夏季气温距平场序列的模方场的拟合效果明显优于EOF分析方法。由此论证了EOF分析方法中资料均匀化订正的必要性,验证了实际分析中AEOF分析方法的较优效果。 相似文献